#160-Digital Billboard Recommendations and …

1 1 digital Billboard Recommendations and Comparisons to conventional billboards by Ian Lewin , FIES, Lighting Sciences, Inc. 7826 East Evans Road Scottsdale, Arizona 85260 Abstract This report summarizes several research projects undertaken related to Billboard lighting. The topics that have been addressed are: Development of digital Billboard luminance Recommendations A comparison of luminances of conventional billboards and digital billboards Sky Glow lumens entering the night sky from conventional and digital billboards . i. digital Billboard Luminance Recommendations Lighting Sciences, Inc.

2 , has undertaken research to develop a method for specification of luminance (brightness) limits for digital billboards based on accepted practice by the Illuminating Engineering Society of North America (IESNA). The recommendation is extremely simple to implement and requires only a footcandle (fc) meter to be used. The research establishes criteria for Billboard luminance limits based on Billboard -to-viewer distances for standardized Billboard categories. For example, a standard Billboard -to-viewer distance of 250 feet is used to establish the Billboard luminance limits for a 14 x 48 foot (672 ) bulletin. The recommended technique is based on accepted IESNA practice for light trespass.

3 Previous outdoor lighting research has documented an established limit on the amount of light arriving at a person s eyes to ensure that the source of the light is not offensive, or worse, potentially dangerous. The technique is simple: the light level at the eye is measured in footcandles and has an upper limit. The limit is low for areas that are generally quite dark, but considerably higher in well lit urban areas. A recommended specification for digital billboards is to use a limit of fc over ambient light conditions. To check if the level is acceptable, a footcandle meter would be held at a height of 5 ft. (which is approximately eye height) and faced towards the Billboard at the desired Billboard -to-viewer distance.

4 A reading of fc or less above ambient light conditions would indicate compliance. It should be noted that the footcandle level produced by the Billboard is characteristic of the Billboard only; because the value of fc is above ambient, it is not affected by whatever the ambient level may be. 2 The standards set forth in the report are based on the worst-case scenario of a driver or pedestrian viewing the display head-on (directly at a 90-degree angle), while in practice most displays are viewed at an angle. Since displays are generally viewed at an angle, the luminance (glare) is substantially reduced. Furthermore, the report provides values for Billboard luminance of different color images and notes that luminance levels are based on a worst-case scenario of an all-white display, which is unlikely to happen, save for a malfunction.

5 Knowing these values, and having established a Billboard luminance limit for a particular Billboard , the allowable percentage of dimming setting is also easily calculated . The investigations and this report do not cover factors related to changing images and Billboard message movement. Issues that may be related to motorist attention are beyond the scope of the work and use of the proposals in this study should be based on that understanding. ii. comparison of conventional and digital Billboard Luminances A study by Rensselaer Polytechnic Institute Lighting Research Center has measured the luminance of typical conventional billboards and has developed the maximum value of luminance that can be expected.

6 LSI has compared the Recommendations developed in this report to the Rensselaer measured values. The digital billboards will be brighter, but only slightly brighter, than the maximum luminance of conventional billboards . iii. Sky Glow Sky glow is caused by lighting at night entering the atmosphere and being scattered by airborne particulates. Sky glow may result from the use of lighting fixtures that emit light above a horizontal plane so that it enters the atmosphere directly. The effect also is caused by light reflecting from lighted objects, such as a road surface, a building or a Billboard . The study has evaluated the amount of light entering the atmosphere from a variety of lighting installations.

7 Measured in "sky lumens," the results allow a comparison to be made of different lighting systems relative to sky glow. Specifically calculations have been made to compare the sky lumens produced by conventional Billboard lighting systems, both three and four luminaire bottom mounted systems lighting a standard 14 x 48ft. Billboard , to the sky lumens caused by roadway and parking lot lighting. Various scenarios have been used for the roadway lighting, combining residential and major highway lighting in a typical neighborhood. Areas have been considered that consist only of roadway lighting, as well as areas that contain both roadway and parking lot lighting.

8 The results of the study support a conclusion that the vast majority of sky glow is a product of urban development. Even where full cut-off fixtures are used on all roadway and parking lot lighting fixtures, and if there is an average of one Billboard per square mile, over 96% of the sky glow produced per urban square mile is from those sources and not Billboard lighting, for the 3conditions examined. For the examples considered, a single three fixture Billboard lighting system produces approximately 2 to 3% of the sky lumens caused by roadway/parking area lighting in the example one square mile area. For a four fixture Billboard lighting system, the range becomes roughly to 4%.

9 These figures can be prorated. For example, if there are two such billboards per square mile, the percentages are doubled; if there is one such Billboard per two square miles, the percentages will be halved. The exact percentages of sky glow are affected by the density of roadways/parking areas, the type of lighting fixtures used and the lighting level provided, among other factors. It is emphasized that the comparisons herein between billboards , roadway and parking lot lighting do not and cannot provide an estimate of the actual percentage of sky glow attributable to billboards . Significant sky glow is produced by multiple other sources such as ball fields, car headlights, floodlighted monuments and buildings, and other outdoor lighting sources.

10 However, it is apparent that for the scenarios considered, the contribution of Billboard lighting to sky glow is small in comparison to that from roadways and parking areas. Excluding these other sources, roadways and parking areas produce 96 to 98% of sky lumens, compared to the 2 to 4% produced per Billboard in the example urban square mile. digital billboards operating at the luminance levels recommended in this report produce much fewer lumens into the night sky than conventional bottom mounted lighting systems. This is primarily due to the elimination of the external luminaires, but also is a result of the characteristics of the Billboard pixel design whereby light in upward directions is reduced in comparison to light sent below the horizontal in the direction of viewers.